I made a new kind of evolution process called Inverso Evolution, which is a special type of evolution that only the starters, including previous starters, as well as Eevee and Riolu, may have. Essentially, once your Pokemon becomes its final evolution, you will have the ability to take it to the Inverso Well- which "devolves" your Pokemon back to its first form, but gives it a new ability called Paragon Aura, which increases the Pokemon's stats by 1+, but it can only activate once per battle. These Pokemon are based on their first stage evolution but with changes to its design that makes them look similar to their third evolution. Their bst also mimic mythic legendary Pokemon (100 across the board), -which is explained in the lore of the well but for now ill leave that part out- but have two negative stats and a positive stat, that have a different of 20 each, but all their HP is 100. For example:
Inverso Bulbasaur: 100 80 100 120 100 80
Inverso Charmander: 100 120 100 80 80 100
Inverso Squirtle: 100 80 120 100 100 80
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Inverso Chickorita: 100 100 80 100 120 80
Inverso Cyndaquil: 100 80 80 120 100 100
Inverso Totodile: 100 120 80 80 100 100
This is still a work in progress and nothing is final. This evolution is tied to the mythical Pokemon of the game, Revenerso, a Ice/Ghost type. The name is a mix of Inverso and Revenant. The idea I had is that a human from long ago tried to bring his Pokemon friend back from the dead using the Inverso Well, but was traumatized by his Pokemon's new, zombified form and abandoned it, leaving Revenerso to become cold to others. It's ability is Inverso Renewel, which makes it stop any fatal attack at 1 hp, then fully heals and gets a boost to all its stats by 1, but it's ability become Empty Heart, which does nothing.
Again, wip.